Getting "The search request was unable to connect to the search service"

 

After crawling successfully and validating that documents were indexed by FAST, you were still unable to search from SharePoint, and receive this error:

The search request was unable to connect to the search service

In ULS we are getting

 

03-28-2011 11:25:05.71 w3wp.exe (0x0B90) 0x1D08 SharePoint Server Search Query g4hx Monitorable FASTSearchRuntime::SendRequest--Search Service Not Found Exception when trying to search FAST backend: Microsoft.Office.Server.Search.Query.SearchServiceNotFoundException: The search request was unable to connect to the Search Service. ---> System.ServiceModel.FaultException`1[Microsoft.Office.Server.Search.Administration.SearchServiceApplicationFault]: The creator of this fault did not specify a Reason. (Fault Detail is equal to Microsoft.Office.Server.Search.Administration.SearchServiceApplicationFault).     --- End of inner exception stack trace ---     at Microsoft.Office.Server.Search.Administration.SearchServiceApplicationProxy.ThrowBackwardCompatibleException(FaultException`1 ex)     at

 

Cause:

The processes responsible for Claims-based authorization in FAST were not able to initialize successfully, with the following seen in the authorization-admin log:

AdminLibrary.dll:MakeRemoteRequestToWorker - Unable to complete request to sam worker node

AdminLibrary.dll:Resuscitate - Unable to get LastCommittedTransactionId

Resolution:

These communication errors were causing by a missing SPN either for the user or the machine name, which we correct with setspn on the domain controller:

setspn -A HTTP/fastmachine DOMAIN\fastuser

setspn -A HTTP/fastmachine.domain.extension DOMAIN\fastuser